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Abstract

Background: Patients with chronic obstructive pulmonary disease (COPD) often have multiple chronic conditions. It has not been previously investigated what proportions of patient-centered outcomes and health care utilization can be attributed to individual chronic conditions that concurrently manifest among patients with asthma, COPD, or both.

Methods: Using data from rounds 1–3 from the cohorts initiated in years 2008–2012 of the Medical Expenditure Panel Survey, we evaluated all patients 40 years and older who had been told by a doctor that they currently had asthma, chronic bronchitis or emphysema. The total sample size was 3,486 patients, and data recorded at round 1 (baseline) were used as explanatory variables for occurrence of each of the seven dichotomous outcomes over a 1-year period corresponding to the time between rounds 1 and 3. Based on multivariable logistic regression, the average attributable fractions (AAFs) for 12 distinct chronic conditions were calculated for three patient-centered outcomes and four health care utilization outcomes. The 12 conditions were: angina, arthritis, asthma, cancer, congestive heart failure, cognitive decline, COPD, diabetes, high blood pressure, lung cancer, myocardial infarction, and stroke. The three patient-centered outcomes were: 7 or more disability days, incident mobility, and incident worsening in perceived health. The four utilization outcomes were: any emergency room (ER) visit, any hospitalization, any outpatient visit, and respiratory hospitalization.

Results: Outcome models –– the models of the seven outcomes exhibited fair to good discrimination (C-statistics between 66% and 76%) and calibration ranging from poor to excellent (Hosmer-Lemeshow P-values from 0.01 to 0.84). Patient-centered outcomes –– the 12 conditions collectively explained the great majority of each of these outcomes. Presented hereafter are the sums of the AAFs from all 12 conditions (followed in parentheses by the four conditions, in descending order, that yielded the largest AAFs of each outcome). The sum of AAFs for 7 or more disability days was 77.8% (arthritis 24.2%, COPD 18.3%, cognitive decline 13.9%, asthma 8.4%). Sum of AAFs for incident mobility was 72.1% (arthritis 29.5%, COPD 10.4%, asthma 10.4%, high blood pressure 6.4%). Sum of AAFs for incident worsening of perceived health was 68% (COPD 21.3%, arthritis 15.4%, high blood pressure 9.4%, asthma 6.8%). Utilization outcomes –– the 12 conditions collectively explained somewhere between a small fraction through a minority of each utilization outcome. Sum of AAFs for any ER Visit was 17.7% (COPD 4.4%, high blood pressure 3.0%, arthritis 2.6%, cognitive decline 2.5%). Sum of AAFs for any hospitalization was 15.6% (COPD 4.3%, arthritis 3.0%, diabetes 2.1%, high blood pressure 2.1%). Sum of AAFs for any outpatient visit was 35% (arthritis 12.8%, high blood pressure 6.1%, asthma 3.9%, cancer 3.3%). Sum of AAFs for respiratory hospitalization was 5% (COPD 4.0%, diabetes 1.0%)

Conclusion: Despite largely similar performance of the underlying multivariable logistic models, the 12 chronic conditions explained a much greater share of the overall occurrence of the patient-centered outcomes than for the utilization outcomes. From among the 12 conditions, arthritis, COPD and asthma consistently account for substantive proportions of outcome events in the patient-centered domain.